Rowan Hart BMedSci (1), Amrey Krause PhD (2), Debbie Alexander BSc (1), Barbara Hauser PhD (1), Barbara Kuske PhD (1), Philip L Riches PhD (1)
Affiliation(s):
1. Rheumatic Diseases Unit, Western General Hospital, NHS Lothian
2. EPCC, The Bayes Centre, University of Edinburgh
Background: Lower urate levels are associated with reduced flare frequency in gout, with a treat-to-target urate approach showing reduction in flares by year two of treatment.1 There are insufficient long-term studies in gout to allow the time to final gout flare to be predicted with confidence.
Objective: To assess predictors at baseline of time to a final gout flare.
Status: This is an exploratory analysis of data from previously completed trials.
Methodology: We have developed a smartphone app (GoutSMART) which encourages patients to maintain a diary of gout flares and urate levels. A randomised controlled feasibility trial in 60 patients showed that use of the GoutSMART app over 1 year helped patients achieve urate targets and reduction in gout flares superior to usual care.2 Furthermore, a 2-year extension of the GoutSMART trial has demonstrated that continued 2-monthly urate monitoring results in cessation of flares in most participants.3 Flares were adjudicated using criteria published by Gaffo et al.4 A regression analysis was performed in participants who reached the end of the extension trial with >12 months flare free investigating the number of days to last flare. To calculate the number of days to final flare, we calculated the difference between the trial start date of a participant, and the date of their final flare. Those participants who did not have a flare since the start date of their trial (i.e the number of days to last flare was 0) were included in the regression analysis.
Findings: By the end of 2 years, 28 (93.3%) of 30 active care participants were flare free compared to 8 (72.7%) of 11 usual care (p=0.052). The average number of days to final flare in the 36 flare-free participants was 259.64 (SD 229.24). In a multiple linear regression analysis that included the number of baseline flares, BMI, age, urate level, number of comorbidities, presence of tophi, colchicine prophylaxis, and sex, the only significant factors predicting the number of days to last flare were the number of baseline flares (p<0.01) and colchicine prophylaxis (p<0.05). In a univariate analysis, the average days to last flare in participants having ≤3 flares a year at baseline was 189 compared to 472 days in those having ≥4 flares (p<0.001). A linear model predicted the number of days to final flare is 87 days multiplied by the number of baseline flares, with an added 33 days. The average number of days to final flare in patients who were on colchicine prophylaxis was 193 (SD 168), compared to 282 (SD 245) for those not on colchicine prophylaxis. However, this was not significant when considering these two variables alone (p=0.319).
Significance: Stratification of patients by the number of flares sustained in the last year leads to more than doubling in the estimated time to cessation of flares. This analysis should help patients make informed decisions around when to start urate lowering therapy. Further research in a larger number of patients is needed to fully determine clinical predictors of time to final flare and investigate the role of colchicine prophylaxis in time to final flare.
References:
1. Doherty M, Jenkins W, Richardson H, Sarmanova A, Abhishek A, Ashton D, Barclay C, Doherty S, Duley L, Hatton R, Rees F, Stevenson M, Zhang W; Efficacy and cost-effectiveness of nurse-led care involving education and engagement of patients and a treat-to-target urate-lowering strategy versus usual care for gout: a randomised controlled trial Lancet. 2018; 10156(392):1403-1412
2. Riches PL, Alexander D, Hauser B, Kuske B, Krause A. Evaluation of supported self-management in gout (GoutSMART): a randomised controlled feasibility trial. The Lancet Rheumatology. 2022 May 1;4(5):e320-8.
3. Riches PL, Alexander D, Brown C, Abbas H, Hart R, Krause A. Evaluation of continued 2-monthly or annual urate monitoring in gout: an extension of the GoutSMART randomised controlled feasibility trial. Explor Musculoskeletal Dis. 2024;2:509–20. https://doi.org/10.37349/emd.2024.00075
4. Gaffo AL, Dalbeth N, Saag KG, Singh JA, Rahn EJ, Mudano AS, et al. Validation of a Definition of Flare in Patients With Established Gout. Arthritis Rheumatol. 2018 Mar;70(3):462-467